Town gas and LP gas are being widely used as an energy source for cooking, heating, hot-water supply, or the like. However, if there is any failure of handling, these gases explode and cause a great accident. On the other hand, recently high altitude and airtight houses have caused the neighborhood to suffer damage from the gas accident. Therefore, putting the safety provision and gas device for prevention of the gas accidents to practical use should be early achieved in view of social conditions.
For prevention of the gas accidents, fuse cocks, reinforced gas hoses, town gas alarm devices, shut-off systems associated with alarm devices, and the like have been hitherto employed. These have not been spread to existing houses because of troublesome installation and are not necessarily effective for explosive accidents with suicidal intent which account for most of the accidents.
Of the causes of gas accidents, short-time great amount discharge of raw gas resulting from the separation of a pipe from a gas cock or the intentional opening of a gas cock and abnormal heating or oxygen deficiency resulting from the forgetting of turning-off of gas equipment important factors for the accidents, the accidents with suicidal intent relating to the former.
In these accidents, the flow rate pattern such as that gas flow rate and continuous time of flow rate becomes abnormal as compared with the normal conditions. Therefore, it is possible to prevent a wide range of gas accident including the accident with suicidal intent by automatically shutting off the gas main when the gas flow rate pattern becomes abnormal. Furthermore, the installation can be improved by combining the system therefor with a gas meter.
The estimation of pattern of use, comparison with an abnormal pattern, and the like can be realized by means of a microcomputer.